<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<meta name="viewport" content="width=device-width, initial-scale=1">
		<title>Title</title>
		<style type="text/css">
			* {
				margin: 0;
				padding: 0;
			}
			ul {
				list-style: none;
			}
			.wrap {
				width: 330px;
				height: 30px;
				margin: 100px auto 0;
				padding-left: 10px;
				background-image: url(imgs/bg.jpg);
			}
			.wrap li {
				background-image: url(imgs/libg.jpg);
			}
			.wrap > ul > li {
				float: left;
				margin-right: 10px;
				position: relative;
			}
			.wrap a {
				display: block;
				height: 30px;
				width: 100px;
				text-decoration: none;
				color: #000;
				line-height: 30px;
				text-align: center;
			}
			.wrap li ul {
				position: absolute;
				top: 30px;
				display: none;
			}
		</style>
		<script src="../jquery-1.12.4.js" type="text/javascript" charset="utf-8"></script>
		<script type="text/javascript">
			$(function(){
				//mouseover: 鼠标经过事件
				//mouseout:  鼠标离开事件
				
				//mouseenter: 鼠标进入事件
				//mouseleave: 鼠标离开事件
				
				var $li = $(".wrap>ul>li");
				
				//给li注册鼠标经过事件,让自己的ul显示出来
				$li.mouseenter(function(){
					//找到所有的儿子,并且还的是ul
					
					//stop: 停止当前正在执行的动画
					$(this).children("ul").stop().slideDown();
					
				});
				$li.mouseleave(function(){
					$(this).children("ul").stop().slideUp();
				});
				
			});
		</script>
	</head>
	<body>
		<div class="wrap">
			<ul>
				<li>
					<a href="javascript:void(0);">一级菜单1</a>
					<ul class="ul">
						<li><a href="javascript:void(0);">二级菜单11</a></li>
						<li><a href="javascript:void(0);">二级菜单12</a></li>
						<li><a href="javascript:void(0);">二级菜单13</a></li>
					</ul>
				</li>
				<li>
					<a href="javascript:void(0);">一级菜单2</a>
					<ul>
						<li><a href="javascript:void(0);">二级菜单21</a></li>
						<li><a href="javascript:void(0);">二级菜单22</a></li>
						<li><a href="javascript:void(0);">二级菜单23</a></li>
					</ul>
				</li>
				<li>
					<a href="javascript:void(0);">一级菜单3</a>
					<ul>
						<li><a href="javascript:void(0);">二级菜单31</a></li>
						<li><a href="javascript:void(0);">二级菜单32</a></li>
						<li><a href="javascript:void(0);">二级菜单33</a></li>
					</ul>
				</li>
			</ul>
		</div>
	</body>
</html>